Securing Drill Motor Coupler

[Ralph Lambert]

We are in the process of building up the drill motor drivetrain per the picture provided by FIRST. It appears that the coupler will unscrew from the drill transmission when turning in one direction. Has anyone had a problem with this? If so, how did you fix it?

[jrgrim12]

there are two left hand screws that are provided. They screw thru the coupler and into the drill shaft. If you don't do this it will unscrew. I forgot to install them and we had that problem right off the bat.

[ChrisH]

BTW treat those left hand screws like gold and be sure to get spares. If you don't, you will need them. When was the last time you saw a left handd screw at your local Home Despot?

If you don't need them at a competition, they will probably have a very high trading value, so keep an eye on yours.

[rbayer]

Originally posted by ChrisH
BTW treat those left hand screws like gold and be sure to get spares. If you don't, you will need them. When was the last time you saw a left handd screw at your local Home Despot?

If you don't need them at a competition, they will probably have a very high trading value, so keep an eye on yours.

Definately agree here. While inventorying our kit, I took these, put them in a little plastice bag and wrote "If you don't know what a left-handed screw is, don't even think of opening this bag". Or something to that effect.

Getting replacements for these is a royal pain, especially on short notice, and without them you're going to have to find some other way to connect the drills.

[Mark Pettit]

Not only did I not find any left-handed screws in our kit, but I am at a loss for where they screw into. I do not see any threaded holes on any of the drill motors or the couplers. Would somebody please take the time to explain what they are and where they go?
Thanks in advance!

[rbayer]

They are small black screws with a blue spot on the shaft. If I remember correctly, they were inside one of the drill mount/coupler bags. Or maybe it was the actual drill bag?

Anyway, if you look at the output shaft of the gearbox, you'll see that it's hollow. The left-handed screw goes in the inner hole. The Aluminum hex piece that screws onto the outside as a hole in it that this screw goes through. It's not threaded, but it is a clearance hole.

--Rob

[Cory]

forget the couplers, well be making our own output shaft after were done prototyping.

Cory

[Mark Pettit]

Thanks! They were right in front of my face the whole time!
:p

[Bash-a-rat]

Ugh.. okay... Um... I have a little question that may be hard to answer... Our team is trying to get longer left handed thread screws, but we need the specs for the screw so we can go get it. These lil boogers really are hard to find... And I couldn't have said it better than this: treat em like gold. We checked the manuals in the kit, etc... If you have the specs or know where to find them, please PM me. Thanks.

[Dick Linn]

One thing I thought we'd do is to drill through one of the flats on the aluminum coupler (without the left-hand screw in place) and 1/2 way through the threaded drill shaft, then use a roll pin to help prevent it from unscrewing. If done correctly, it would not significantly weaken the threaded part on the drill, yet would serve as a backup to the left-hand screw and the friction of the aluminum shaft adapter threads. I hate to think of using a serious type of Lock-Tite in case I have to get that puppy apart.

[Madison]

Originally posted by Dick Linn
One thing I thought we'd do is to drill through one of the flats on the aluminum coupler (without the left-hand screw in place) and 1/2 way through the threaded drill shaft, then use a roll pin to help prevent it from unscrewing. If done correctly, it would not significantly weaken the threaded part on the drill, yet would serve as a backup to the left-hand screw and the friction of the aluminum shaft adapter threads. I hate to think of using a serious type of Lock-Tite in case I have to get that puppy apart.

Similarly, we are putting a flat onto the drill output shaft and then pinning our coupler alongside the flat.

We'll use the threads to couple the motor to our shaft, and the pin ought to prevent it from unscrewing.

[rbayer]

If you use the left-handed screw properly, you do not need to pin anything. In fact, most hand-drills use this same system for attaching the Chuck to the output shaft, and they don't even have that blue spray on their screws! As far as I can tell, the blue stuff acts vaguely like Ny-Lock, making it nearly impossible for the screws to work themselves loose.

A note: make sure the Aluminum piece is as far down as it can turn and that the left-handed screw is flush with the top of the aluminum. It takes a LOT of power to get the left-handed screws the last .5-.25" down, but you need to do it. We destroyed two allen wrenches doing it, but I assure you they aren't going anywhere.

[Alvin]

Anyone know the specs for those left-handed screws, or where they might be found? I don't seem to be able to find them in the kit, unfortunately, so I might need to try to purchase some.

[Gadget470]

Skill Bosch Left Handed Screw (http://www2.usfirst.org/2003comp/Specs/SB_lh_screw.pdf)

[AKGirl]

If not for finding this we would have come up with a much scarier plan, so thanx

AKGirl

[Robb Gerber]

We've discovered that not all couplers are made alike.

With two drill motors installed we noticed that one had a slight
wobble. After some close inspection we noticed that the coupler that screws onto the drill shaft was defective.
The peice was not drilled in the center. This caused the
deflection on the end of the transmission shaft.
We called a team down the road and got their two couplers
(Thanks Team 188 - Blizzard!). Back at home base we
screwed these in and while they're better, they're still not perfect.
So now we've got 3 and all of them a different. I put in the best one and spun up the motor. Its a lot better than before. In fact,
it'll have to do because I'm stuck with these cruddy couplers.
(I wish I used lovejoy couplers)

One one else experience this?

[Eric Bareiss]

Ours wobble too. I think that FIRST drilled them wrong.

[Alvin]

Same here. I should hope that that does not create a significant problem or anything.

I wonder what happened to our 2nd left-handed screw; it seems as though it never came in the kit. Had to get a replacement from MMH.